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Tejun Heo151060a2009-04-14 10:54:54 +09001/*
2 * CUSE: Character device in Userspace
3 *
4 * Copyright (C) 2008-2009 SUSE Linux Products GmbH
5 * Copyright (C) 2008-2009 Tejun Heo <tj@kernel.org>
6 *
7 * This file is released under the GPLv2.
8 *
9 * CUSE enables character devices to be implemented from userland much
10 * like FUSE allows filesystems. On initialization /dev/cuse is
11 * created. By opening the file and replying to the CUSE_INIT request
12 * userland CUSE server can create a character device. After that the
13 * operation is very similar to FUSE.
14 *
15 * A CUSE instance involves the following objects.
16 *
17 * cuse_conn : contains fuse_conn and serves as bonding structure
18 * channel : file handle connected to the userland CUSE server
19 * cdev : the implemented character device
20 * dev : generic device for cdev
21 *
22 * Note that 'channel' is what 'dev' is in FUSE. As CUSE deals with
23 * devices, it's called 'channel' to reduce confusion.
24 *
25 * channel determines when the character device dies. When channel is
26 * closed, everything begins to destruct. The cuse_conn is taken off
27 * the lookup table preventing further access from cdev, cdev and
28 * generic device are removed and the base reference of cuse_conn is
29 * put.
30 *
31 * On each open, the matching cuse_conn is looked up and if found an
32 * additional reference is taken which is released when the file is
33 * closed.
34 */
35
36#include <linux/fuse.h>
37#include <linux/cdev.h>
38#include <linux/device.h>
39#include <linux/file.h>
40#include <linux/fs.h>
41#include <linux/kdev_t.h>
42#include <linux/kthread.h>
43#include <linux/list.h>
44#include <linux/magic.h>
45#include <linux/miscdevice.h>
46#include <linux/mutex.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090047#include <linux/slab.h>
Tejun Heo151060a2009-04-14 10:54:54 +090048#include <linux/spinlock.h>
49#include <linux/stat.h>
50
51#include "fuse_i.h"
52
53#define CUSE_CONNTBL_LEN 64
54
55struct cuse_conn {
56 struct list_head list; /* linked on cuse_conntbl */
57 struct fuse_conn fc; /* fuse connection */
58 struct cdev *cdev; /* associated character device */
59 struct device *dev; /* device representing @cdev */
60
61 /* init parameters, set once during initialization */
62 bool unrestricted_ioctl;
63};
64
65static DEFINE_SPINLOCK(cuse_lock); /* protects cuse_conntbl */
66static struct list_head cuse_conntbl[CUSE_CONNTBL_LEN];
67static struct class *cuse_class;
68
69static struct cuse_conn *fc_to_cc(struct fuse_conn *fc)
70{
71 return container_of(fc, struct cuse_conn, fc);
72}
73
74static struct list_head *cuse_conntbl_head(dev_t devt)
75{
76 return &cuse_conntbl[(MAJOR(devt) + MINOR(devt)) % CUSE_CONNTBL_LEN];
77}
78
79
80/**************************************************************************
81 * CUSE frontend operations
82 *
83 * These are file operations for the character device.
84 *
85 * On open, CUSE opens a file from the FUSE mnt and stores it to
86 * private_data of the open file. All other ops call FUSE ops on the
87 * FUSE file.
88 */
89
90static ssize_t cuse_read(struct file *file, char __user *buf, size_t count,
91 loff_t *ppos)
92{
93 loff_t pos = 0;
94
95 return fuse_direct_io(file, buf, count, &pos, 0);
96}
97
98static ssize_t cuse_write(struct file *file, const char __user *buf,
99 size_t count, loff_t *ppos)
100{
101 loff_t pos = 0;
102 /*
103 * No locking or generic_write_checks(), the server is
104 * responsible for locking and sanity checks.
105 */
106 return fuse_direct_io(file, buf, count, &pos, 1);
107}
108
109static int cuse_open(struct inode *inode, struct file *file)
110{
111 dev_t devt = inode->i_cdev->dev;
112 struct cuse_conn *cc = NULL, *pos;
113 int rc;
114
115 /* look up and get the connection */
116 spin_lock(&cuse_lock);
117 list_for_each_entry(pos, cuse_conntbl_head(devt), list)
118 if (pos->dev->devt == devt) {
119 fuse_conn_get(&pos->fc);
120 cc = pos;
121 break;
122 }
123 spin_unlock(&cuse_lock);
124
125 /* dead? */
126 if (!cc)
127 return -ENODEV;
128
129 /*
130 * Generic permission check is already done against the chrdev
131 * file, proceed to open.
132 */
133 rc = fuse_do_open(&cc->fc, 0, file, 0);
134 if (rc)
135 fuse_conn_put(&cc->fc);
136 return rc;
137}
138
139static int cuse_release(struct inode *inode, struct file *file)
140{
141 struct fuse_file *ff = file->private_data;
142 struct fuse_conn *fc = ff->fc;
143
144 fuse_sync_release(ff, file->f_flags);
145 fuse_conn_put(fc);
146
147 return 0;
148}
149
150static long cuse_file_ioctl(struct file *file, unsigned int cmd,
151 unsigned long arg)
152{
153 struct fuse_file *ff = file->private_data;
154 struct cuse_conn *cc = fc_to_cc(ff->fc);
155 unsigned int flags = 0;
156
157 if (cc->unrestricted_ioctl)
158 flags |= FUSE_IOCTL_UNRESTRICTED;
159
160 return fuse_do_ioctl(file, cmd, arg, flags);
161}
162
163static long cuse_file_compat_ioctl(struct file *file, unsigned int cmd,
164 unsigned long arg)
165{
166 struct fuse_file *ff = file->private_data;
167 struct cuse_conn *cc = fc_to_cc(ff->fc);
168 unsigned int flags = FUSE_IOCTL_COMPAT;
169
170 if (cc->unrestricted_ioctl)
171 flags |= FUSE_IOCTL_UNRESTRICTED;
172
173 return fuse_do_ioctl(file, cmd, arg, flags);
174}
175
176static const struct file_operations cuse_frontend_fops = {
177 .owner = THIS_MODULE,
178 .read = cuse_read,
179 .write = cuse_write,
180 .open = cuse_open,
181 .release = cuse_release,
182 .unlocked_ioctl = cuse_file_ioctl,
183 .compat_ioctl = cuse_file_compat_ioctl,
184 .poll = fuse_file_poll,
185};
186
187
188/**************************************************************************
189 * CUSE channel initialization and destruction
190 */
191
192struct cuse_devinfo {
193 const char *name;
194};
195
196/**
197 * cuse_parse_one - parse one key=value pair
198 * @pp: i/o parameter for the current position
199 * @end: points to one past the end of the packed string
200 * @keyp: out parameter for key
201 * @valp: out parameter for value
202 *
203 * *@pp points to packed strings - "key0=val0\0key1=val1\0" which ends
204 * at @end - 1. This function parses one pair and set *@keyp to the
205 * start of the key and *@valp to the start of the value. Note that
206 * the original string is modified such that the key string is
207 * terminated with '\0'. *@pp is updated to point to the next string.
208 *
209 * RETURNS:
210 * 1 on successful parse, 0 on EOF, -errno on failure.
211 */
212static int cuse_parse_one(char **pp, char *end, char **keyp, char **valp)
213{
214 char *p = *pp;
215 char *key, *val;
216
217 while (p < end && *p == '\0')
218 p++;
219 if (p == end)
220 return 0;
221
222 if (end[-1] != '\0') {
223 printk(KERN_ERR "CUSE: info not properly terminated\n");
224 return -EINVAL;
225 }
226
227 key = val = p;
228 p += strlen(p);
229
230 if (valp) {
231 strsep(&val, "=");
232 if (!val)
233 val = key + strlen(key);
234 key = strstrip(key);
235 val = strstrip(val);
236 } else
237 key = strstrip(key);
238
239 if (!strlen(key)) {
240 printk(KERN_ERR "CUSE: zero length info key specified\n");
241 return -EINVAL;
242 }
243
244 *pp = p;
245 *keyp = key;
246 if (valp)
247 *valp = val;
248
249 return 1;
250}
251
252/**
253 * cuse_parse_dev_info - parse device info
254 * @p: device info string
255 * @len: length of device info string
256 * @devinfo: out parameter for parsed device info
257 *
258 * Parse @p to extract device info and store it into @devinfo. String
259 * pointed to by @p is modified by parsing and @devinfo points into
260 * them, so @p shouldn't be freed while @devinfo is in use.
261 *
262 * RETURNS:
263 * 0 on success, -errno on failure.
264 */
265static int cuse_parse_devinfo(char *p, size_t len, struct cuse_devinfo *devinfo)
266{
267 char *end = p + len;
268 char *key, *val;
269 int rc;
270
271 while (true) {
272 rc = cuse_parse_one(&p, end, &key, &val);
273 if (rc < 0)
274 return rc;
275 if (!rc)
276 break;
277 if (strcmp(key, "DEVNAME") == 0)
278 devinfo->name = val;
279 else
280 printk(KERN_WARNING "CUSE: unknown device info \"%s\"\n",
281 key);
282 }
283
284 if (!devinfo->name || !strlen(devinfo->name)) {
285 printk(KERN_ERR "CUSE: DEVNAME unspecified\n");
286 return -EINVAL;
287 }
288
289 return 0;
290}
291
292static void cuse_gendev_release(struct device *dev)
293{
294 kfree(dev);
295}
296
297/**
298 * cuse_process_init_reply - finish initializing CUSE channel
299 *
300 * This function creates the character device and sets up all the
301 * required data structures for it. Please read the comment at the
302 * top of this file for high level overview.
303 */
304static void cuse_process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
305{
306 struct cuse_conn *cc = fc_to_cc(fc);
307 struct cuse_init_out *arg = &req->misc.cuse_init_out;
308 struct page *page = req->pages[0];
309 struct cuse_devinfo devinfo = { };
310 struct device *dev;
311 struct cdev *cdev;
312 dev_t devt;
313 int rc;
314
315 if (req->out.h.error ||
316 arg->major != FUSE_KERNEL_VERSION || arg->minor < 11) {
317 goto err;
318 }
319
320 fc->minor = arg->minor;
321 fc->max_read = max_t(unsigned, arg->max_read, 4096);
322 fc->max_write = max_t(unsigned, arg->max_write, 4096);
323
324 /* parse init reply */
325 cc->unrestricted_ioctl = arg->flags & CUSE_UNRESTRICTED_IOCTL;
326
327 rc = cuse_parse_devinfo(page_address(page), req->out.args[1].size,
328 &devinfo);
329 if (rc)
330 goto err;
331
332 /* determine and reserve devt */
333 devt = MKDEV(arg->dev_major, arg->dev_minor);
334 if (!MAJOR(devt))
335 rc = alloc_chrdev_region(&devt, MINOR(devt), 1, devinfo.name);
336 else
337 rc = register_chrdev_region(devt, 1, devinfo.name);
338 if (rc) {
339 printk(KERN_ERR "CUSE: failed to register chrdev region\n");
340 goto err;
341 }
342
343 /* devt determined, create device */
344 rc = -ENOMEM;
345 dev = kzalloc(sizeof(*dev), GFP_KERNEL);
346 if (!dev)
347 goto err_region;
348
349 device_initialize(dev);
350 dev_set_uevent_suppress(dev, 1);
351 dev->class = cuse_class;
352 dev->devt = devt;
353 dev->release = cuse_gendev_release;
354 dev_set_drvdata(dev, cc);
355 dev_set_name(dev, "%s", devinfo.name);
356
357 rc = device_add(dev);
358 if (rc)
359 goto err_device;
360
361 /* register cdev */
362 rc = -ENOMEM;
363 cdev = cdev_alloc();
364 if (!cdev)
365 goto err_device;
366
367 cdev->owner = THIS_MODULE;
368 cdev->ops = &cuse_frontend_fops;
369
370 rc = cdev_add(cdev, devt, 1);
371 if (rc)
372 goto err_cdev;
373
374 cc->dev = dev;
375 cc->cdev = cdev;
376
377 /* make the device available */
378 spin_lock(&cuse_lock);
379 list_add(&cc->list, cuse_conntbl_head(devt));
380 spin_unlock(&cuse_lock);
381
382 /* announce device availability */
383 dev_set_uevent_suppress(dev, 0);
384 kobject_uevent(&dev->kobj, KOBJ_ADD);
385out:
386 __free_page(page);
387 return;
388
389err_cdev:
390 cdev_del(cdev);
391err_device:
392 put_device(dev);
393err_region:
394 unregister_chrdev_region(devt, 1);
395err:
396 fc->conn_error = 1;
397 goto out;
398}
399
400static int cuse_send_init(struct cuse_conn *cc)
401{
402 int rc;
403 struct fuse_req *req;
404 struct page *page;
405 struct fuse_conn *fc = &cc->fc;
406 struct cuse_init_in *arg;
407
408 BUILD_BUG_ON(CUSE_INIT_INFO_MAX > PAGE_SIZE);
409
410 req = fuse_get_req(fc);
411 if (IS_ERR(req)) {
412 rc = PTR_ERR(req);
413 goto err;
414 }
415
416 rc = -ENOMEM;
417 page = alloc_page(GFP_KERNEL | __GFP_ZERO);
418 if (!page)
419 goto err_put_req;
420
421 arg = &req->misc.cuse_init_in;
422 arg->major = FUSE_KERNEL_VERSION;
423 arg->minor = FUSE_KERNEL_MINOR_VERSION;
424 arg->flags |= CUSE_UNRESTRICTED_IOCTL;
425 req->in.h.opcode = CUSE_INIT;
426 req->in.numargs = 1;
427 req->in.args[0].size = sizeof(struct cuse_init_in);
428 req->in.args[0].value = arg;
429 req->out.numargs = 2;
430 req->out.args[0].size = sizeof(struct cuse_init_out);
431 req->out.args[0].value = &req->misc.cuse_init_out;
432 req->out.args[1].size = CUSE_INIT_INFO_MAX;
433 req->out.argvar = 1;
434 req->out.argpages = 1;
435 req->pages[0] = page;
436 req->num_pages = 1;
437 req->end = cuse_process_init_reply;
438 fuse_request_send_background(fc, req);
439
440 return 0;
441
442err_put_req:
443 fuse_put_request(fc, req);
444err:
445 return rc;
446}
447
448static void cuse_fc_release(struct fuse_conn *fc)
449{
450 struct cuse_conn *cc = fc_to_cc(fc);
451 kfree(cc);
452}
453
454/**
455 * cuse_channel_open - open method for /dev/cuse
456 * @inode: inode for /dev/cuse
457 * @file: file struct being opened
458 *
459 * Userland CUSE server can create a CUSE device by opening /dev/cuse
460 * and replying to the initilaization request kernel sends. This
461 * function is responsible for handling CUSE device initialization.
462 * Because the fd opened by this function is used during
463 * initialization, this function only creates cuse_conn and sends
464 * init. The rest is delegated to a kthread.
465 *
466 * RETURNS:
467 * 0 on success, -errno on failure.
468 */
469static int cuse_channel_open(struct inode *inode, struct file *file)
470{
471 struct cuse_conn *cc;
472 int rc;
473
474 /* set up cuse_conn */
475 cc = kzalloc(sizeof(*cc), GFP_KERNEL);
476 if (!cc)
477 return -ENOMEM;
478
479 fuse_conn_init(&cc->fc);
480
481 INIT_LIST_HEAD(&cc->list);
482 cc->fc.release = cuse_fc_release;
483
484 cc->fc.connected = 1;
485 cc->fc.blocked = 0;
486 rc = cuse_send_init(cc);
487 if (rc) {
488 fuse_conn_put(&cc->fc);
489 return rc;
490 }
491 file->private_data = &cc->fc; /* channel owns base reference to cc */
492
493 return 0;
494}
495
496/**
497 * cuse_channel_release - release method for /dev/cuse
498 * @inode: inode for /dev/cuse
499 * @file: file struct being closed
500 *
501 * Disconnect the channel, deregister CUSE device and initiate
502 * destruction by putting the default reference.
503 *
504 * RETURNS:
505 * 0 on success, -errno on failure.
506 */
507static int cuse_channel_release(struct inode *inode, struct file *file)
508{
509 struct cuse_conn *cc = fc_to_cc(file->private_data);
510 int rc;
511
512 /* remove from the conntbl, no more access from this point on */
513 spin_lock(&cuse_lock);
514 list_del_init(&cc->list);
515 spin_unlock(&cuse_lock);
516
517 /* remove device */
518 if (cc->dev)
519 device_unregister(cc->dev);
520 if (cc->cdev) {
521 unregister_chrdev_region(cc->cdev->dev, 1);
522 cdev_del(cc->cdev);
523 }
524
525 /* kill connection and shutdown channel */
526 fuse_conn_kill(&cc->fc);
527 rc = fuse_dev_release(inode, file); /* puts the base reference */
528
529 return rc;
530}
531
532static struct file_operations cuse_channel_fops; /* initialized during init */
533
534
535/**************************************************************************
536 * Misc stuff and module initializatiion
537 *
538 * CUSE exports the same set of attributes to sysfs as fusectl.
539 */
540
541static ssize_t cuse_class_waiting_show(struct device *dev,
542 struct device_attribute *attr, char *buf)
543{
544 struct cuse_conn *cc = dev_get_drvdata(dev);
545
546 return sprintf(buf, "%d\n", atomic_read(&cc->fc.num_waiting));
547}
548
549static ssize_t cuse_class_abort_store(struct device *dev,
550 struct device_attribute *attr,
551 const char *buf, size_t count)
552{
553 struct cuse_conn *cc = dev_get_drvdata(dev);
554
555 fuse_abort_conn(&cc->fc);
556 return count;
557}
558
559static struct device_attribute cuse_class_dev_attrs[] = {
560 __ATTR(waiting, S_IFREG | 0400, cuse_class_waiting_show, NULL),
561 __ATTR(abort, S_IFREG | 0200, NULL, cuse_class_abort_store),
562 { }
563};
564
565static struct miscdevice cuse_miscdev = {
566 .minor = MISC_DYNAMIC_MINOR,
567 .name = "cuse",
568 .fops = &cuse_channel_fops,
569};
570
571static int __init cuse_init(void)
572{
573 int i, rc;
574
575 /* init conntbl */
576 for (i = 0; i < CUSE_CONNTBL_LEN; i++)
577 INIT_LIST_HEAD(&cuse_conntbl[i]);
578
579 /* inherit and extend fuse_dev_operations */
580 cuse_channel_fops = fuse_dev_operations;
581 cuse_channel_fops.owner = THIS_MODULE;
582 cuse_channel_fops.open = cuse_channel_open;
583 cuse_channel_fops.release = cuse_channel_release;
584
585 cuse_class = class_create(THIS_MODULE, "cuse");
586 if (IS_ERR(cuse_class))
587 return PTR_ERR(cuse_class);
588
589 cuse_class->dev_attrs = cuse_class_dev_attrs;
590
591 rc = misc_register(&cuse_miscdev);
592 if (rc) {
593 class_destroy(cuse_class);
594 return rc;
595 }
596
597 return 0;
598}
599
600static void __exit cuse_exit(void)
601{
602 misc_deregister(&cuse_miscdev);
603 class_destroy(cuse_class);
604}
605
606module_init(cuse_init);
607module_exit(cuse_exit);
608
609MODULE_AUTHOR("Tejun Heo <tj@kernel.org>");
610MODULE_DESCRIPTION("Character device in Userspace");
611MODULE_LICENSE("GPL");